Scientists have watched as the melting of Greenland's ice has accelerated

Governments should consider setting lower targets for levels of CO2 in the atmosphere and investigate ways to extract surplus amounts of the greenhouse gas from circulation, say climate scientists.

Before the industrial revolution, the level of CO2 in the atmosphere was around 280 parts per million by volume (ppmv) but that has risen to around 380ppmv due to our burning of fossil fuels.

The Intergovernmental Panel on Climate Change is focusing its efforts on emission scenarios that lead to concentrations of no less than 450ppmv while the UK government is working towards a concentration target of around double pre-industrial levels, at 550ppmv.

If concentrations stabilise at 550ppmv, the corresponding global average temperature rise brought about by the greenhouse effect could still be as high as 5.5C, sufficient to melt the Greenland Ice Sheet and prompt a rise in sea level of six metres.

Fair targets

Scientists speaking here at EuroScience Open Forum 2004 said governments should be exploring the potential of Negative Emissions Technologies (NETs) which could actively remove CO2 from the atmosphere and stabilise atmospheric concentrations of the gas at much lower levels.

"The current stabilisation targets are a social construction," said Professor Christian Azar, of Goteborg University's Department of Physical Resource Theory.

"Governments are not looking at NETs because part of the cost of doing so will fall on certain industry sectors and they are powerful enough to protest."

Current CO2 emissions vary greatly between countries of the developed and developing world.

In 1998, the US released 5.4 tonnes of carbon per capita, European countries averaged around 1.9 tonnes and Africa emitted 0.3 tonnes.

To meet a global concentration target of about 350-400ppmv would require a cross-the-board emission level of no more than 0.4 tonnes of carbon per person per year.

In the developed world this would require per capita emissions to be cut to the level of Africa or Asia, while the people of the developing world would never be able to use the same amount of fossil fuels that the industrialised countries have to achieve the equivalent standard of living.

The proposal closely resembles an idea developed by the UK-based Global Commons Institute, which has gained wide support among scientists and policymakers, called contraction and convergence.

"Contraction" means cutting the world's output of greenhouse gases, and "convergence" means sharing out between countries the amount of climate pollution which scientists say the Earth can tolerate, so that by perhaps 2050 everyone in the world is entitled to emit the same amount of pollution.

Leakage rules

NETs offer a means of cutting emissions without the need for immediate extreme lifestyle changes.

They ideally involve using biomass from planted forests to produce energy and then capturing the CO2 produced, or alternatively extracting CO2 directly from the atmosphere.

Recovered CO2 would then be injected into deep underground or sub-sea stores to remove it from circulation.

Opponents of the technologies suggest such methods would be costly and that CO2 could still leak back into the environment, with unknown consequences.

However, modelling the various options for achieving emissions targets of between 350ppmv and 450ppmv between 1990 and 2200 at the least cost, Professor Azar found not only that it was feasible but that in certain cases the cost barely exceeded that of running large fossil fuel plants.

"The capture and storage of CO2 offers a great opportunity to get lower stabilisation targets at lower cost," he said.

"We need a regulatory framework on how to deal with carbon capture and storage. It should include rules for leakage and how to deal with capture from biomass.

"We also need to support technological development so that solar and other renewables can come to the marketplace and become viable options."